An AC surface-discharge plasma display panel (hereinafter, abbreviated as “panel”) as a typical AC type plasma display panel is configured by a front panel including a glass substrate on which scan electrodes and sustain electrodes between which surface discharge occurs are formed in lines, and a back panel including a glass substrate on which data electrodes are formed in lines. The front panel and the back panel are disposed parallel and oppositely to each other such that the electrodes on both panels are in a matrix form, in addition, discharge spaces are formed in a gap between them, and sealed at their outer circumferential portions with a sealing material such as glass frit. Between the front panel and the back panel, discharge cells are provided, the cells being divided by barrier ribs formed on the back panel. Phosphor layers are formed on inner wall surfaces of cell spaces divided by the barrier ribs. In the panel having such a configuration, ultra-violet rays are generated by gas discharge, and the ultra-violet rays excite the phosphor layers of respective colors of red (R), green (G), and blue (B) to emit visible light for color display.
In the panel, one field period is divided into a plurality of subfields, and subfields for emission are selected and combined to drive the panel for gray-scale display. Each subfield includes an initialization period, a writing period, and a sustaining period. To display image data, different signal waveforms are applied to the respective electrodes in the initialization period, writing period, and sustaining period respectively.
In the initialization period, for example, positive pulse voltage are applied to all the scan electrodes, so that necessary wall charge is accumulated on a protective layer on a dielectric layer covering the scan electrodes and the sustain electrodes and on the phosphor layers. In addition, priming particles (priming for discharge, that is, excitation particles) are generated in the period, the particles being for reducing delay in discharge to stably induce writing discharge.
In the writing period, negative scan pulses are sequentially applied to all the scan electrodes for scanning the electrodes. While scanning the scan electrodes, positive writing pulse voltage is applied to data electrodes corresponding to discharge cells to be displayed according to display data. Writing discharge is induced between the data electrodes applied with the positive writing pulse voltage and the scan electrodes, and writing wall charge is thus formed on a surface of the protective layer on the scan electrodes. At that time, since the writing voltage is applied to all the data electrodes configuring display cells, in which the writing discharge is to be induced, at the same time, on one scan electrode, all the writing discharge to be induced is induced at a time, causing flow of discharge current. Therefore, voltage drop due to impedance of the scan electrodes and a drive circuit becomes large. As a result, there is a difficulty that stable writing discharge is hard.
In the next sustaining period, a voltage pulse sufficient to keep the discharge is applied between the scan electrodes and the sustain electrodes. This induces sustaining discharge in the discharge cells having the writing wall charge formed therein. Then, discharge plasma is generated between the scan electrodes and the sustain electrodes, and the phosphor layers are excited and thus emit light for a certain period by ultraviolet rays caused by the discharge plasma. At that time, in discharge cells that were not applied with the writing pulse voltage during writing, discharge is not induced and the phosphor layers are not excited and thus do not emit light.
In such a panel, there is a difficulty that large delay in discharge occurs in writing discharge in a subsequent writing period in the subfields, consequently writing operation becomes unstable.
To overcome the difficulties, a technique has been proposed, in which the data electrodes are divided into at least two data electrode groups, and timing of applying the writing voltage to the data electrodes in the writing period is varied by setting time difference between the data electrode groups. As such a technique in the related art, a technique in Japanese Patent Unexamined Publication No. 8-305319 is known.
In the technique, the data electrodes are divided into two data electrode groups, and time difference is set in timing of applying writing pulse voltage to respective data electrode groups in a writing period, so that time difference exists in timing of starting writing discharge corresponding to respective data electrode groups. In this way, discharge current flowing into the scan electrodes in writing discharge is temporarily dispersed. As a result, compared with a case that all writing discharge is induced at a time on one scan electrode, a peak value of the discharge current flowing into the scan electrode can be controlled low. Therefore, voltage drop can be controlled to stabilize applied voltage to respective discharge cells, consequently stable discharge can be realized, the voltage drop being caused by impedance in a circuit of driving the scan electrodes or metal wires forming the scan electrodes.
However, in the related art as described above, the writing discharge must be induced in a surely separated manner to sufficiently reduce the peak value of the discharge current. To this end, sufficient time difference must be set in timing of applying writing pulse voltage to the data electrode groups respectively. As a result, there is a difficulty that writing time is set long, resulting in increase in time taken for the writing period.
Particularly, in a panel having increased resolution, time to be set for the writing period is increased with increase in number of scan electrodes. As a result, time to be set for the sustaining period needs to be decreased, consequently a difficulty of decrease in peak luminance arises. Therefore, in such a panel, a subject is given, that is, the writing time needs to be reduced to the utmost so that time for the sustaining period is secured.